Currently, the illumination of homes, offices, classrooms and factories are mostly provided by fluorescent lamp tubes. In use, the incandescent bulbs are not such convenient as the fluorescent lamp tubes. However, the incandescent bulbs are still used in many situations to help in illumination as necessary. The fluorescent lamp tube is a glass tube body containing therein mercury and argon. Wolfram filament electrodes are sealed in the light caps at two ends of the tube body. After powered on, the wolfram filament electrodes can emit ultraviolet ray to energy the fluorescent powder coated on the inner wall face of the tube body so as to emit visible light. With respect to the incandescent bulb, the wolfram filament is sealed in the glass bulb. After powered, the wolfram filament is heated and incandesced to emit visible light. The prices of the fluorescent lamp tube and the incandescent bulb are both not very high. However, when the light core structure formed of the wolfram filament is powered on to emit light, the light core structure will consume quite a lot of electricity. Moreover, the mercury contained in the fluorescent lamp tube will contaminate the environment.
Therefore, from the viewpoint of energy saving and environmental protection, adoption of light-emitting diode (LED) is a very good substitution option for the conventional fluorescent lamp tube and incandescent bulb. However, before using the LED light to fully replace the incandescent bulb and fluorescent lamp tube, a problem must be overcome. That is, in the conventional LED light core structure, the LEDs are disposed on a printed circuit board. The printed circuit board is nontransparent. Therefore, in the case that the LEDs are disposed on the same face of the printed circuit board, the LED can only project light in one single direction without the possibility of 360-degree illumination. In the case that the LEDs are arranged on both faces of the printed circuit board, a 360-degree illumination effect can be achieved. However, the cost for the LED light core structure will be increased. Moreover, the light emitted from the LED on one face of the printed circuit board cannot pass through the printed circuit board to the other face thereof. Under such circumstance, the energy is wasted.
In view of the above, an improved LED light core structure has been developed. In the LED light core structure, the LEDs are disposed on a transparent substrate made of sapphire. The LEDs are arranged on one face of the sapphire substrate and the anodes and cathodes of the LEDs are connected to outer side of the LED light via fine metal leads for connecting with a power supply to power the LEDs. The light emitted from the LEDs can pass through the sapphire substrate to illuminate both sides of the sapphire substrate and achieve a 360-degree illumination effect.
However, in manufacturing, transfer and use process of the LED light core, the sapphire substrate is very likely to crack and break. Therefore, the ratio of good products is lowered. Moreover, the sapphire substrate has relatively poor heat conductivity. Therefore, the sapphire substrate can hardly provide good heat dissipation effect for the LED. As a result, the LED often burns down due to overheating. Accordingly, the reliability of the product is unstable. In addition, the sapphire substrate is an electrical insulator. Therefore, it is necessary to add metal electrodes to the positive and negative electrodes. It often takes place that the metal electrodes detach from the sapphire substrate. This further lowers the ratio of good products in the manufacturing process.
It is therefore tried by the applicant to provide an LED light core structure to overcome the above problems of the conventional LED light core structure.